Watch: videos from Brussels attacks. Belgium on high terror alert

Nearly 20 people were killed in three explosions in Brussels, Belgium, according to Reuters reports. Ten people were killed at the Maelbeek police station near European Union headquarters and 13 were killed at the airport, according to public broadcaster VRT.

Brussels police spokesman Christian De Coninck told AP: "There are victims, serious injury, people have died. I have no idea yet on the numbers of injured or dead."

The terror threat level in Belgium has been raised to four, its highest level. Raising the threat level to four means authorities can deploy the army onto the streets to meet security needs, CNN reports.

France's top security officials have said the country is reinforcing security at airports, train stations and metros after Tuesday's attacks.

Interior Minister Bernard Cazeneuve said France has stepped up security following news of the attacks.